Systems and methods for lenticular laser incision

ABSTRACT

Embodiments of this invention generally relate to ophthalmic laser procedures and, more particularly, to systems and methods for lenticular laser incision. In an embodiment, an ophthalmic surgical laser system comprises a laser delivery system for delivering a pulsed laser beam to a target in a subject&#39;s eye, an XY-scan device to deflect the pulsed laser beam, a Z-scan device to modify a depth of a focus of the pulsed laser beam, and a controller configured to form a top lenticular incision and a bottom lenticular incision of a lens in the subject&#39;s eye, where each of the top and bottom lenticular incision includes a center concave portion and an edge transition portion that has a smooth convex shape and is smoothly joined to the center concave portion.

RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. § 120 of U.S.application Ser. No. 16/109,654, filed Aug. 22, 2018, which is acontinuation-in-part under 35 U.S.C. § 120 of U.S. application Ser. No.14/865,396, filed Sep. 25, 2015, which is a non-provisional applicationand claims the benefit under 35 U.S.C. § 119(e) of U.S. ProvisionalApplication Ser. No. 62/055,437, filed Sep. 25, 2014 and 62/183,653,filed Jun. 23, 2015. All of the above-mentioned applications areincorporated herein in their entirety as if fully set forth.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of this invention relate generally to laser-assistedophthalmic procedures, and more particularly, to systems and methods forlenticular incisions in the cornea.

Description of Related Art

Vision impairments such as myopia (near-sightedness), hyperopia andastigmatism can be corrected using eyeglasses or contact lenses.Alternatively, the cornea of the eye can be reshaped surgically toprovide the needed optical correction. Eye surgery has becomecommonplace with some patients pursuing it as an elective procedure toavoid using contact lenses or glasses to correct refractive problems,and others pursuing it to correct adverse conditions such as cataracts.And, with recent developments in laser technology, laser surgery isbecoming the technique of choice for ophthalmic procedures. The reasoneye surgeons prefer a surgical laser beam over manual tools likemicrokeratomes and forceps is that the laser beam can be focusedprecisely on extremely small amounts of ocular tissue, thereby enhancingaccuracy and reliability of the procedure. These in turn enable betterwound healing and recovery following surgery.

Hyperopia (far-sightedness) is a visual impairment where light enteringthe eye does not focus at the retina to produce a sharp image asdesired, but rather focuses at a location behind the retina such that apatient sees a blurred disc. The basic principle to treating hyperopiais to add positive focusing power to the cornea. For instance, ahyperopic eye can be treated by placing a convex lens in front of theeye to add a positive focusing power to the eye. After correction, lightpassing through the convex lens and into the eye focuses at the retinato form a sharp image.

Different laser eye surgical systems use different types of laser beamsfor the various procedures and indications. These include, for instance,ultraviolet lasers, infrared lasers, and near-infrared, ultra-shortpulsed lasers. Ultra-short pulsed lasers emit radiation with pulsedurations as short as 10 femtoseconds and as long as 3 nanoseconds, anda wavelength between 300 nm and 3000 nm. Examples of laser systems thatprovide ultra-short pulsed laser beams include the Abbott Medical OpticsiFS Advanced Femtosecond Laser, the IntraLase FS Laser, and OptiMedica'sCatalys Precision Laser System.

Prior surgical approaches for reshaping the cornea include laserassisted in situ keratomileusis (hereinafter “LASIK”), photorefractivekeratectomy (hereinafter “PRK”) and Small Incision Lens Extraction(hereinafter “SmILE”).

In the LASIK procedure, an ultra-short pulsed laser is used to cut acorneal flap to expose the corneal stroma for photoablation withultraviolet beams from an excimer laser. Photoablation of the cornealstroma reshapes the cornea and corrects the refractive condition such asmyopia, hyperopia, astigmatism, and the like.

It is known that if part of the cornea is removed, the pressure exertedon the cornea by the aqueous humor in the anterior chamber of the eyewill act to close the void created in the cornea, resulting in areshaped cornea. By properly selecting the size, shape and location of acorneal void, one can obtain the desired shape, and hence, the desiredoptical properties of the cornea.

In current laser surgery treatments that correct hyperopia using LASIKand PRK, positive focusing power is added to the cornea by steepeningthe curvature of the cornea, by for example, removing a ring-shapedstroma material from the cornea. In a LASIK procedure, a flap is firstcreated, then lifted up for the ring-shaped stroma material to beremoved or ablated away by an excimer laser. The center of the cornea isnot removed while more outward portions of the cornea are removed. Theflap is then put back into place. The cornea thus steepens due to thevoid created in the cornea. Common patterns that steepen the corneainclude ring, tunnel and toric shapes. LASIK can typically correcthyperopia for up to 5D (diopter). In a PRK procedure where no flap iscreated, the epithelium layer is first removed, and the ring-shapedstroma material is then removed by an excimer laser. The epitheliumlayer will grow back within a few days after the procedure.

Recently, surgeons have started using another surgical technique otherthan LASIK and PRK for refractive correction. Instead of ablatingcorneal tissue with an excimer laser following the creation of a cornealflap, the newer SmILE technique involves tissue removal with twofemtosecond laser incisions that intersect to create a lenticule forextraction. Lenticular extractions can be performed either with orwithout the creation of a corneal flap. With the flapless procedure, arefractive lenticule is created in the intact portion of the anteriorcornea and removed through a small incision.

In the SmILE procedure illustrated in FIG. 10, a femtolaser 110 is usedto make a side cut 120, an upper surface cut 130 and a lower surface cut140 that forms a cut lens 150. A tweezer, for example, is then used toextract the cut lens beneath the anterior surface of the cornea 160through the side cut 120. Recently, SmILE has been applied to treatmyopia by cutting and extracting a convex lens-shaped stroma materialwith a femtosecond laser. However, SmILE techniques have not beenapplied in treating hyperopia.

Furthermore, as shown in FIG. 1, conventional femtosecond laser surgerysystems generate a curved dissection surface to make a lenticularincision by scanning a laser focus on the intended dissection surfacethrough a XY-scanning device and a Z-scanning device. This method doesnot use the more advantageous “fast-scan-slow-sweep” scanning schemewith femtosecond lasers having high repetition rate (“rep rate”), fore.g., in the MHz range. Using the “fast-scan-slow-sweep” scanning schemefor a lenticular incision, however, will generate vertical “steps” andwill require many vertical side cuts, resulting in a lenticulardissection surface that is not smooth.

Therefore, there is a need for improved systems and methods to generatecorneal lenticular incisions for high repetition rate femtosecond lasersto correct hyperopia.

SUMMARY OF THE INVENTION

Hence, to obviate one or more problems due to limitations anddisadvantages of the related art, this disclosure provides embodimentsincluding an ophthalmic surgical laser system comprising a laserdelivery system for delivering a pulsed laser beam to a target in asubject's eye, an XY-scan device to deflect the pulsed laser beam, aZ-scan device to modify a depth of a focus of the pulsed laser beam, anda controller configured to form a top lenticular incision and a bottomlenticular incision of a lens on the subject's eye. The XY-scan devicedeflects the pulsed laser beam to form a scan line. The scan line istangential to the parallels of latitude of the lens. The scan line isthen moved along the meridians of longitude of the lens. The toplenticular incision is moved over the top surface of the lens throughthe apex of the top surface of the lens, and the bottom lenticularincision is moved over the bottom surface of the lens through the apexof bottom surface of the lens.

Other embodiments disclose an ophthalmic surgical laser systemcomprising a laser delivery system for delivering a pulsed laser beam toa target in a subject's eye, an XY-scan device to deflect the pulsedlaser beam, a Z-scan device to modify a depth of a focus of the pulsedlaser beam, and a controller configured to form a top concave lenticularincision and a bottom concave lenticular incision of a lens on thesubject's eye.

In one aspect, embodiments of the present invention provide anophthalmic surgical laser system, which includes: a laser deliverysystem for delivering a pulsed laser beam to a target in a subject'seye; an XY-scan device to deflect the pulsed laser beam; a Z-scan deviceto modify a depth of a focus of the pulsed laser beam; and a controllerconfigured to control the XY-scan device and the Z-scan device to form atop lenticular incision and a bottom lenticular incision of a lens in acornea of the subject's eye, wherein the top lenticular incision has atop convex spherical portion at a center and a top edge transitionportion that surrounds the top spherical portion, the top sphericalportion being a part of a first sphere, the top edge transition portionbeing not a part of the first sphere and being located within a volumedefined by the first sphere, the top lenticular incision being a smoothsurface, wherein the bottom lenticular incision has a bottom convexspherical portion at a center and a bottom edge transition portion thatsurrounds the bottom spherical portion, the bottom spherical portionbeing a part of a second sphere, the bottom edge transition portionbeing not a part of the second sphere and being located within a volumedefined by the second sphere, the bottom lenticular incision being asmooth surface, wherein the top and bottom edge transition portions aremirror symmetrical to each other with respect to a transverse centerplane perpendicular to an optical axis of the eye, and wherein the topand bottom edge transition portions intersect each other at anintersection location and both extend beyond the intersection location.

In another aspect, embodiments of the present invention provide a methodfor creating a lenticular incision using an ophthalmic surgical lasersystem, the method including the steps of: generating a pulsed laserbeam; delivering the pulsed laser beam to a target in a subject's eye;deflecting, by an XY-scan device, the pulsed laser beam; modifying, by aZ-scan device, a depth of a focus of the pulsed laser beam; andcontrolling, by a controller, the XY-scan device and the Z-scan deviceto form a top lenticular incision and a bottom lenticular incision of alens in a cornea of the subject's eye, wherein the top lenticularincision has a top spherical portion at a center and a top edgetransition portion that surrounds the top spherical portion, the topspherical portion being a part of a first sphere, the top edgetransition portion being not a part of the first sphere and beinglocated within a volume defined by the first sphere, the top lenticularincision being a smooth surface, wherein the bottom lenticular incisionhas a bottom spherical portion at a center and a bottom edge transitionportion that surrounds the bottom spherical portion, the bottomspherical portion being a part of a second sphere, the bottom edgetransition portion being not a part of the second sphere and beinglocated within a volume defined by the second sphere, the bottomlenticular incision being a smooth surface, wherein the top and bottomedge transition portions are mirror symmetrical to each other withrespect to a transverse center plane perpendicular to an optical axis ofthe eye, and wherein the top and bottom edge transition portionsintersect each other at an intersection location and both extend beyondthe intersection location.

In some embodiments, in a side cross-sectional view, the top edgetransition portion is a part of an ellipse, and the bottom edgetransition portion is a part of another ellipse.

This summary and the following detailed description are merelyexemplary, illustrative, and explanatory, and are not intended to limit,but to provide further explanation of the invention as claimed.Additional features and advantages of the invention will be set forth inthe descriptions that follow, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription, claims and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages will be facilitated by referring to the following detaileddescription that sets forth illustrative embodiments using principles ofthe invention, as well as to the accompanying drawings, in which likenumerals refer to like parts throughout the different views. Like parts,however, do not always have like reference numerals. Further, thedrawings are not drawn to scale, and emphasis has instead been placed onillustrating the principles of the invention. All illustrations areintended to convey concepts, where relative sizes, shapes, and otherdetailed attributes may be illustrated schematically rather thandepicted literally or precisely.

FIG. 1 illustrates a conventional lenticular cut via scanning a singlefocus spot.

FIG. 2 is a simplified diagram of a surgical ophthalmic laser systemaccording to an embodiment of the present invention.

FIG. 3 is another simplified diagram of a surgical ophthalmic lasersystem according to an embodiment of the present invention.

FIG. 4 is a simplified diagram of a controller of a surgical ophthalmiclaser system according to an embodiment of the present invention.

FIG. 5 illustrates an exemplary scanning of a surgical ophthalmic lasersystem according to an embodiment of the present invention.

FIG. 6 illustrates an exemplary lenticular incision using afast-scan-slow-sweep scheme of a surgical ophthalmic laser systemaccording to an embodiment of the present invention.

FIG. 7 illustrates a geometric relation between a fast scan line and anintended spherical dissection surface of a surgical ophthalmic lasersystem according to an embodiment of the present invention.

FIG. 8 illustrates an exemplary lenticular incision using a surgicalophthalmic laser system according to an embodiment of the presentinvention.

FIG. 9 is a flowchart illustrating a process according to an embodimentof the present invention.

FIG. 10 illustrates a conventional Small Incision Lenticule Extractionprocedure.

FIG. 11 illustrates a hypothetical Small Incision Lenticule Extractionprocedure.

FIG. 12 illustrates an exemplary lenticular incision process accordingto an embodiment of the present invention.

FIG. 13 illustrates an exemplary lenticular incision using a surgicalophthalmic laser system according to an embodiment of the presentinvention.

FIG. 14 illustrates an exemplary scanning process using a surgicalophthalmic laser system according to an embodiment of the presentinvention.

FIG. 15 is a flowchart illustrating an exemplary surgery processaccording to an embodiment of the present invention.

FIG. 16 illustrates an exemplary lenticular incision using a surgicalophthalmic laser system according to another embodiment of the presentinvention.

FIGS. 17A and 17B illustrate a conventional Small Incision LenticuleExtraction procedure.

FIG. 18 is a flowchart illustrating an exemplary surgery processaccording to an embodiment of the present invention.

FIG. 19 illustrates a part of a lenticular incision according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of this invention are generally directed to systems andmethods for laser-assisted ophthalmic procedures, and more particularly,to systems and methods for lenticular laser incisions.

Referring to the drawings, FIG. 2 shows a system 10 for making anincision in a material 12. The system 10 includes, but is not limitedto, a laser 14 capable of generating a pulsed laser beam 18, an energycontrol module 16 for varying the pulse energy of the pulsed laser beam18, a Z-scanner 20 for modifying the depth of the pulse laser beam 18, acontroller 22, a prism 23 (e.g., a Dove or Pechan prism, or the like),and an XY-scanner 28 for deflecting or directing the pulsed laser beam18 from the laser 14 on or within the material 12. The controller 22,such as a processor operating suitable control software, is operativelycoupled with the Z-scanner 20, the XY-scanner 28, and the energy controlunit 16 to direct a scan line 30 of the pulsed laser beam along a scanpattern on or in the material 12. In this embodiment, the system 10further includes a beam splitter 26 and a detector 24 coupled to thecontroller 22 for a feedback control mechanism (not shown) of the pulsedlaser beam 18. Other feedback methods may also be used, including butnot necessarily limited to position encoder on the scanner 20, or thelike. In an embodiment, the pattern of pulses may be summarized inmachine readable data of tangible storage media in the form of atreatment table. The treatment table may be adjusted according tofeedback input into the controller 22 from an automated image analysissystem in response to feedback data provided from an ablation monitoringsystem feedback system (not shown).

Optionally, the feedback may be manually entered into the controller 22by a system operator. The feedback may also be provided by integrating awavefront measurement system (not shown) with the laser surgery system10. The controller 22 may continue and/or terminate a sculpting orincision in response to the feedback, and may also modify the plannedsculpting or incision based at least in part on the feedback.Measurement and imaging systems are further described in U.S. Pat. Nos.6,315,413 and 8,260,024, the complete disclosures of which areincorporated herein by reference.

In an embodiment, the system 10 uses a pair of scanning mirrors or otheroptics (not shown) to angularly deflect and scan the pulsed laser beam18. For example, scanning mirrors driven by galvanometers may beemployed where each of the mirrors scans the pulsed laser beam 18 alongone of two orthogonal axes. A focusing objective (not shown), whetherone lens or several lenses, images the pulsed laser beam 18 onto a focalplane of the system 10. The focal point of the pulsed laser beam 18 maythus be scanned in two dimensions (e.g., the x-axis and the y-axis)within the focal plane of the system 10. Scanning along the thirddimension, i.e., moving the focal plane along an optical axis (e.g., thez-axis), may be achieved by moving the focusing objective, or one ormore lenses within the focusing objective, along the optical axis.

Laser 14 may comprise a femtosecond laser capable of providing pulsedlaser beams, which may be used in optical procedures, such as localizedphotodisruption (e.g., laser induced optical breakdown). Localizedphotodisruptions can be placed at or below the surface of the materialto produce high-precision material processing. For example, amicro-optics scanning system may be used to scan the pulsed laser beamto produce an incision in the material, create a flap of the material,create a pocket within the material, form removable structures of thematerial, and the like. The term “scan” or “scanning” refers to themovement of the focal point of the pulsed laser beam along a desiredpath or in a desired pattern.

In other embodiments, the laser 14 may comprise a laser sourceconfigured to deliver an ultraviolet laser beam comprising a pluralityof ultraviolet laser pulses capable of photodecomposing one or moreintraocular targets within the eye.

Although the laser system 10 may be used to photoalter a variety ofmaterials (e.g., organic, inorganic, or a combination thereof), thelaser system 10 is suitable for ophthalmic applications in someembodiments. In these cases, the focusing optics direct the pulsed laserbeam 18 toward an eye (for example, onto or into a cornea) for plasmamediated (for example, non-UV) photoablation of superficial tissue, orinto the stroma of the cornea for intrastromal photodisruption oftissue. In these embodiments, the surgical laser system 10 may alsoinclude a lens to change the shape (for example, flatten or curve) ofthe cornea prior to scanning the pulsed laser beam 18 toward the eye.

The laser system 10 is capable of generating the pulsed laser beam 18with physical characteristics similar to those of the laser beamsgenerated by a laser system disclosed in U.S. Pat. Nos. 4,764,930,5,993,438, and U.S. patent application Ser. No. 12/987,069, filed Jan.7, 2011, which are incorporated herein by reference.

FIG. 3 shows another exemplary diagram of the laser system 10. FIG. 3shows a moveable XY-scanner (or XY-stage) 28 of a miniaturizedfemtosecond laser system. In this embodiment, the system 10 uses afemtosecond oscillator, or a fiber oscillator-based low energy laser.This allows the laser to be made much smaller. The laser-tissueinteraction is in the low-density-plasma mode. An exemplary set of laserparameters for such lasers include pulse energy in the 50-100 nJ rangeand pulse repetitive rates (or “rep rates”) in the 5-20 MHz range. Afast-Z scanner 20 and a resonant scanner 21 direct the laser beam 18 tothe prism 23. When used in an ophthalmic procedure, the system 10 alsoincludes a patient interface 31 design that has a fixed cone nose and aportion that engages with the patient's eye. A beam splitter is placedinside the cone of the patient interface to allow the whole eye to beimaged via visualization optics. In one embodiment, the system 10 uses:optics with a 0.6 numerical aperture (NA) which would produce 1.1 μmFull Width at Half Maximum (FWHM) focus spot size; and a resonantscanner 21 that produces 1-2 mm scan line with the XY-scanner scanningthe resonant scan line to a 10 mm field. The prism 23 rotates theresonant scan line in any direction on the XY plane. The fast-Z scanner20 sets the incision depth and produces a side cut. The system 10 mayalso include an auto-Z module 32 to provide depth reference. Theminiaturized femtosecond laser system 10 may be a desktop system so thatthe patient sits upright while being under treatment. This eliminatesthe need of certain opto-mechanical arm mechanism(s), and greatlyreduces the complexity, size, and weight of the laser system.Alternatively, the miniaturized laser system may be designed as aconventional femtosecond laser system, where the patient is treatedwhile lying down.

FIG. 4 illustrates a simplified block diagram of an exemplary controller22 that may be used by the laser system 10 according to an embodiment ofthis invention. Controller 22 typically includes at least one processor52 which may communicate with a number of peripheral devices via a bussubsystem 54. These peripheral devices may include a storage subsystem56, comprising a memory subsystem 58 and a file storage subsystem 60,user interface input devices 62, user interface output devices 64, and anetwork interface subsystem 66. Network interface subsystem 66 providesan interface to outside networks 68 and/or other devices. Networkinterface subsystem 66 includes one or more interfaces known in thearts, such as LAN, WLAN, Bluetooth, other wire and wireless interfaces,and so on.

User interface input devices 62 may include a keyboard, pointing devicessuch as a mouse, trackball, touch pad, or graphics tablet, a scanner,foot pedals, a joystick, a touch screen incorporated into a display,audio input devices such as voice recognition systems, microphones, andother types of input devices. In general, the term “input device” isintended to include a variety of conventional and proprietary devicesand ways to input information into controller 22.

User interface output devices 64 may include a display subsystem, aprinter, a fax machine, or non-visual displays such as audio outputdevices. The display subsystem may be a flat-panel device such as aliquid crystal display (LCD), a light emitting diode (LED) display, atouchscreen display, or the like. The display subsystem may also providea non-visual display such as via audio output devices. In general, theterm “output device” is intended to include a variety of conventionaland proprietary devices and ways to output information from controller22 to a user.

Storage subsystem 56 can store the basic programming and data constructsthat provide the functionality of the various embodiments of the presentinvention. For example, a database and modules implementing thefunctionality of the methods of the present invention, as describedherein, may be stored in storage subsystem 56. These software modulesare generally executed by processor 52. In a distributed environment,the software modules may be stored on a plurality of computer systemsand executed by processors of the plurality of computer systems.

Storage subsystem 56 typically comprises memory subsystem 58 and filestorage subsystem 60.

Memory subsystem 58 typically includes a number of memories including amain random access memory (RAM) 70 for storage of instructions and dataduring program execution and a read only memory (ROM) 72 in which fixedinstructions are stored. File storage subsystem 60 provides persistent(non-volatile) storage for program and data files. File storagesubsystem 60 may include a hard disk drive along with associatedremovable media, a Compact Disk (CD) drive, an optical drive, DVD,solid-state memory, and/or other removable media. One or more of thedrives may be located at remote locations on other connected computersat other sites coupled to controller 22. The modules implementing thefunctionality of the present invention may be stored by file storagesubsystem 60.

Bus subsystem 54 provides a mechanism for letting the various componentsand subsystems of controller 22 communicate with each other as intended.The various subsystems and components of controller 22 need not be atthe same physical location but may be distributed at various locationswithin a distributed network. Although bus subsystem 54 is shownschematically as a single bus, alternate embodiments of the bussubsystem may utilize multiple busses.

Due to the ever-changing nature of computers and networks, thedescription of controller 22 depicted in FIG. 4 is intended only as anexample for purposes of illustrating only one embodiment of the presentinvention. Many other configurations of controller 22, having more orfewer components than those depicted in FIG. 4, are possible.

As should be understood by those of skill in the art, additionalcomponents and subsystems may be included with laser system 10. Forexample, spatial and/or temporal integrators may be included to controlthe distribution of energy within the laser beam, as described in U.S.Pat. No. 5,646,791, which is incorporated herein by reference. Ablationeffluent evacuators/filters, aspirators, and other ancillary componentsof the surgical laser system are known in the art, and may be includedin the system. In addition, an imaging device or system may be used toguide the laser beam. Further details of suitable components ofsubsystems that can be incorporated into an ophthalmic laser system forperforming the procedures described here can be found incommonly-assigned U.S. Pat. Nos. 4,665,913, 4,669,466, 4,732,148,4,770,172, 4,773,414, 5,207,668, 5,108,388, 5,219,343, 5,646,791,5,163,934, 8,394,084, 8,403,921, 8,690,862, 8,709,001, U.S. applicationSer. No. 12/987,069, filed Jan. 7, 2011, and U.S. application Ser. No.13/798,457 filed Mar. 13, 2013, which are incorporated herein byreference.

In an embodiment, the laser surgery system 10 includes a femtosecondoscillator-based laser operating in the MHz range, for example, 10 MHz,for example, from several MHz to tens of MHz. For ophthalmicapplications, the XY-scanner 28 may utilize a pair of scanning mirrorsor other optics (not shown) to angularly deflect and scan the pulsedlaser beam 18. For example, scanning mirrors driven by galvanometers maybe employed, each scanning the pulsed laser beam 18 along one of twoorthogonal axes. A focusing objective (not shown), whether one lens orseveral lenses, images the pulsed laser beam onto a focal plane of thelaser surgery system 10. The focal point of the pulsed laser beam 18 maythus be scanned in two dimensions (e.g., the X-axis and the Y-axis)within the focal plane of the laser surgery system 10. Scanning along athird dimension, i.e., moving the focal plane along an optical axis(e.g., the Z-axis), may be achieved by moving the focusing objective, orone or more lenses within the focusing objective, along the opticalaxis. It is noted that in many embodiments, the XY-scanner 28 deflectsthe pulse laser beam 18 to form a scan line.

In other embodiments, the beam scanning can be realized with a“fast-scan-slow-sweep” scanning scheme. The scheme consists of twoscanning mechanisms: first, a high frequency fast scanner is used toproduce a short, fast scan line (e.g., a resonant scanner 21 of FIG. 3);second, the fast scan line is slowly swept by much slower X, Y, and Zscan mechanisms. FIG. 5 illustrates a scanning example of a laser system10 using an 8 kHz resonant scanner 21 to produce a scan line of about 1mm and a scan speed of about 25 m/sec, and X, Y, and Z scan mechanismswith the scan speed smaller than 0.1 m/sec. The fast scan line may beperpendicular to the optical beam propagation direction, i.e., it isalways parallel to the XY plane. The trajectory of the slow sweep can beany three dimensional curve drawn by the X, Y, and Z scanning devices(e.g., XY-scanner 28 and Z-scanner 20). An advantage of the“fast-scan-slow-sweep” scanning scheme is that it only uses small fieldoptics (e.g., a field diameter of 1.5 mm) which can achieve high focusquality at relatively low cost. The large surgical field (e.g., a fielddiameter of 10 mm or greater) is achieved with the XY-scanner, which maybe unlimited. In another embodiment shown in FIG. 6, the laser system 10creates a smooth lenticular cut using the “fast-scan-slow-sweep”scanning scheme under a preferred procedure. First, in a threedimensional lenticular cut, the fast scan line is preferably placedtangential to the parallels of latitude 610. For example, in theminiaturized flap maker laser system 10 of FIG. 3, this can be realizedby adjusting a prism 23 to the corresponding orientations via software,e.g., via the controller 22. Second, the slow sweep trajectorypreferably moves along the meridians of longitude 620. For example, inthe miniaturized flap maker system of FIG. 3, this can be done bycoordinating the XY scanner 28, and the Fast-Z scanner 20 via thesoftware, e.g., via the controller 22. The procedure starts with thescan line being parallel to the XY plane, and sweeps through the apex ofthe lens, following the curvature with the largest diameter (see alsoFIG. 8). With this preferred procedure, there are no vertical “steps” inthe dissection, and vertical side cuts are eliminated. As will beanalyzed herein below, the deviations between the laser focus locationsand the intended spherical surface dissections are also minimized.

FIG. 7 shows the geometric relation between the fast scan line 710 andthe intended spherical dissection surface 720, e.g., of a lens,especially the distance deviation (δ) between the end point B of thescan line 720 and point A on the intended dissection surface 720. Themaximum deviation.delta. is the distance between point A and point B,and is given by

$\begin{matrix}{{\delta = {{\sqrt{R^{2} + \frac{L^{2}}{4}} - R} \approx \frac{L^{2}}{8R}}},,} & {{equation}\mspace{14mu} (1)}\end{matrix}$

where R is greater than L. R is the radius of curvature of the surfacedissection 720, and L is the length of the fast scan.

In an exemplary case of myopic correction, the radius of curvature ofthe surface dissection may be determined by the amount of correction,ΔD, using the following equation

$\begin{matrix}{{{\Delta D} = {\frac{\left( {n - 1} \right)}{R_{1}} + \frac{\left( {n - 1} \right)}{R_{2}}}},,} & {{equation}\mspace{14mu} (2)}\end{matrix}$

where n=1.376, which is the refractive index of cornea, and R₁ and R₂(may also be referred herein as Rt and Rb) are the radii of curvaturefor the top surface and bottom surface of a lenticular incision,respectively. For a lenticular incision with R₁=R₂=R (the two dissectionsurface are equal for them to physically match and be in contact), wehave

$\begin{matrix}{{R = \frac{2\left( {n - 1} \right)}{\Delta D}},.} & {{equation}\mspace{14mu} (3)}\end{matrix}$

In an embodiment, FIG. 8 shows an exemplary lenticular incision 900 forextraction using the laser system 10. FIG. 8 shows an exemplarycross-sectional view 910 illustrating a patient interface 905 (orpatient interface 31 as shown in FIG. 3), cornea 906, and lenticularincision volume 915, which will be referred herein as lens to beextracted. Rt and Rb are the radii of curvature for the top surface andbottom surface of a lenticular incision, respectively. ZFt (Zt) is thedepth of the top surface of the lenticular incision. ZFb (Zb) is thedepth of the bottom surface of the lenticular incision. The Z depths maybe calculated based on the respective radii. LT is the lens thickness atthe lens apex, or center thickness of the lens. ZA is depth of the lensapex. DL is the diameter of the lenticular incision, or the lens.{Z_SLOW=0} is the Z reference position before the laser system 10calculates and sets Z_SLOW, e.g., {Z_SLOW=ZA+LT/2} the center depth ofthe lens, which remains fixed for the duration of the incisionprocedure. Z_SLOW may then be the reference position for the Z-scannerfor top and bottom incision surfaces. In an embodiment, the diameter ofthe lens may be received from an operator of the laser system 10, or maybe calculated by the laser system 10. The thickness of the lens may bedetermined, for example, by the total amount of correction (e.g.,diopter) and the diameter of the lens.

A top view 950 of the lenticular incision 900 illustrates threeexemplary sweeps (1A to 1B), (2A to 2B) and (3A to 3B), with each sweepgoing through (i.e., going over) the lenticular incision apex 955. Theincision, or cut, diameter 957 (D_(CUT)) should be equal to or greaterthan the to-be-extracted lenticular incision diameter 917 (DL). A topview 980 shows the top view of one exemplary sweep. In an embodiment,the lenticular incision is performed in the following steps:

1. Calculate the radius of curvature based on the amount of correction,e.g., a myopic correction.

2. Select the diameter for the lenticular incision to be extracted.

3. Perform the side incision first (not shown) to provide a vent for gasthat can be produced in the lenticular surface dissections. This is alsothe incision for the entry of forceps and for lens extraction.

4. Perform bottom surface dissection (the lower dissection as shown incross-sectional view 910). In doing so, the fast scan line is preferablykept tangential to the parallels of latitude, and the trajectory of theslow sweep drawn by X, Y, and Z scanning devices moves along themeridians of longitude (near south pole in a sequence of 1A→1B (firstsweep of lenticular cut), 2A→2B (second sweep of lenticular cut), 3A→3B(third sweep of lenticular cut), and so on, until the full bottomdissection surface is generated.

5. Perform the top surface dissection (the upper dissection as shown inthe cross-sectional view 910) in a similar manner as the bottomdissection is done. It is noted that the bottom dissection is donefirst. Otherwise, the bubble generated during the top dissection willblock the laser beam in making the bottom dissection.

For illustrative purposes, in a myopic correction of ΔD=10 diopter(i.e., 1/m), using equation (3), R=75.2 mm, which is indeed much greaterthan the length L of the fast scan. Assuming a reasonable scan linelength of L=1 mm, using equation (1), the deviation δ=1.7 μm. Thisdeviation is thus very small. For comparison purpose, the depth of focusof a one micron (FWHM) spot size at 1 μm wavelength is about ±3 μm,meaning the length of focus is greater than the deviation δ.

FIG. 9 illustrates a process 1000 of the laser system 10 according to anembodiment. The laser system 10 may start a surgical procedureperforming pre-operation measurements (Action Block 1010). For example,in an ophthalmologic surgery for myopic correction, the myopic diopteris determined, the SLOW_Z position is determined, and so on. The lasersystem 10 calculates the radius of curvature based on the amount ofcorrection, e.g., the myopic correction determined in pre-operationmeasurements (Action Block 1020), as shown, for example, in equations(2) and (3) above. The laser system 10 calculates the diameter of theincision (Action Block 1030), as shown by D_(CUT) in FIG. 8. D_(CUT) isequal to or greater than the diameter of the to-be-extracted lenticule(DL in FIG. 8). The laser system 10 first performs side incision toprovide a vent for gas that can be produced in the lenticular surfacedissections, and for tissue extraction later on (Action Block 1040). Thelaser system 10 then performs the bottom lenticular surface dissection(Action Block 1050) before performing the top lenticular surfacedissection (Action Block 1060). The lenticular tissue is then extracted(Action Block 1070).

In other embodiments, the laser system 10 may also be used to produceother three-dimensional surface shapes, including toric surfaces forcorrecting hyperopia and astigmatism. The laser system 10 may also beused for laser material processing and micromachining for othertransparent materials. Correction of hyperopia by the laser system 10 isdiscussed in detail below.

Conventional laser surgery methods to correct hyperopia utilize cutpatterns including ring-shaped incision patterns that steepen thecurvature of a cornea. However, FIG. 11 illustrates why utilizing thesepatterns using SmILE is impractical and unfeasible. The cross-sectionalview of the cornea 160 in FIG. 11 includes a sidecut 120, an uppersurface cut 130, lower surface cut 140 and a ring-shaped cut 170generated by a SmILE procedure. However, the cornea 160 maintains anuncut annular center portion 180 that remains attached to an anteriorportion and posterior portion of the cornea 160.

This cut pattern is geometrically problematic as the clean removal ofthe ring cut 170 through the side cut 120 as a single ring is impeded bythe center portion 180. Whereas a flap provided in a LASIK procedureallows a ring shape to be easily extracted, the use of a sidecut withouta flap prevents the ring-shaped stroma material from being extractedfrom the tunnel like incision without breaking apart. Thus, aring-shaped lenticule is not suitable for correcting hyperopia using theSmILE procedure since the ring cut 170 will break up unpredictablyduring removal through the side cut 120.

Some LASIK procedures correct hyperopia by removing cornea stromamaterial to increase the steepness of the cornea. For example, outwardportions of the cornea are cut and removed while a center portionremains untouched except for the flap. Once the flap is folded backover, the flap fills the void vacated by the removed cornea stromamaterial and merges with the cornea. The cornea thus becomes steeper anda desired vision correction is achieved. However, the curve of the flapdoes not match the curve of the cornea such that the merger of the flapand cornea creates folds in the stroma that increase light scatteringand create undesirable aberrations.

The inventions described herein overcome these limitations. FIG. 12illustrates an exemplary lenticular incision 1200 that steepens thecornea by cutting and removing a symmetric concave lens-shaped stromamaterial from a cornea 1240. From an optical focus power perspective,the concave shape of the lenticule 1220 is equivalent to steepening thecornea or adding a convex lens in front of the eye.

Furthermore, extraction of the lenticule 1220 as a whole piece through asidecut incision 1210 is assured and improved over a ring-shape cut, ora tunnel-like cut, or a toric cut. The incision includes a peripheralportion 1230 or tapering portion providing ideal merging of the corneaafter the lenticule 1220 is extracted without folding in a top surfaceor bottom surface.

FIG. 13 illustrates an exemplary lenticular incision 1300 using asurgical ophthalmic laser system according to an embodiment of thepresent invention. For example, SmILE techniques may be applied inconjunction with FIG. 13 to treat hyperopia using a sub-nanosecondlaser. A cross-sectional view 1302 and top view 1304 are provided of thelenticule cuts 1310, 1320 and side cut 1350. In FIG. 13, a patientinterface 1340 is pressed against a cornea 1306. The lenticular incisionincludes a bottom lens surface 1310 and a top lens surface 1320. Thebottom surface 1310 includes a radius of curvature R1 and the topsurface 1320 includes a radius of curvature R2.

A side cut 1350 is performed first to provide a path for gas to vent toprevent the formation of bubbles. A bottom surface cut 1310 is thenperformed prior to performing a top surface cut 1320 to prevent thecutting beam from being blocked by bubbles generated by previous corneadissection. The top and bottom surface cuts each include a centralportion and a peripheral portion. The central portions are concave whilethe peripheral portions of the top and bottom cuts tapers (diminishes)towards each other to meet. The tapering peripheral portions minimizelight scattering at the edges and further optimizes the matching of thecut surfaces and prevent folding after the lenticule has been removed.

As shown in FIG. 13, the thickest portion of the cut is provided at theboundary of the taper portion and the concave portion. For the top andbottom surfaces to match after lens extraction, the bottom and topsurfaces are preferably mirror symmetric about a plane 1360.

These exemplary lenticular incisions allow lenticular tissue to beextracted in a single unbroken piece through the sidecut. The taper ofthe peripheral portions allows smooth extraction through the sidecut asa gradual slope is provided. The peripheral portions also support themerging of the top and bottom portions of the cornea as a top surfaceand bottom surface compress back together to form a smooth merge.Without a taper to the peripheral portions, the apex of the centralportions would never merge and would form a permanent gap.

A concave lens cut includes a top concave lenticular incision and abottom concave lenticular incision of a lens in the subject's eye. Theconcave lens cut may include at least one of a spherical surface, acylindrical component, and any high order component. The top concavelenticular incision and the bottom concave lenticular incision may bemirror symmetric or nearly mirror symmetric to each other so long as themerging of the top surface and bottom surface does not create folding.

The system may operate with a laser having a wavelength in a rangebetween 350 nanometer and 1100 nanometer and a pulse width in a rangebetween 10 femtosecond and 1 nanosecond.

In prior art solutions, a top layer cut is longer than a bottom layercut. Under this configuration, the top and bottom cornea portions do notideally merge as the top surface must fold in and compress in order tomerge with shorter layer cut. With this fold created by the dissection,light scattering is increased. In contrast, a mirror symmetric cut alonga center line allows ideal merge with no folding between a top layer andbottom layer. Consequently, there is less light scattering.

A lens edge thickness is given by δ_(E), δ_(E1), δ_(E2). A lens depth His given as a distance between an anterior of the cornea 1306 and theplane 1360. The bottom surface 1310 and top surface 1320 have a lensdiameter D_(L), a lens center thickness .delta.c and a shape defined byrespective curves Z_(1,L(x,y)) and Z_(2,L(x,y)). In order to minimizethe amount of dissected cornea stroma material removed, the centralthickness .delta.c should be minimized. For example, the centralthickness may be a few μm, which can be achieved by using a laser beamwith a high numerical aperture (such as NA=0.6).

Each of the bottom lens surface cut 1310 and the top lens surface cut1320 includes a tapering zone 1330 along a periphery of the cuts. Thetapering zone 1330 is defined by a tapering zone width and the curvesZ_(1,T(x,y)) and Z_(2,T(x,y)).

A sidecut 1350 is provided from a surface of the cornea to the taperingzone 1330 for removal of the lenticule. The sidecut may meet thetapering zone 1330 on the mirror plane 1360 or other suitable extractionpoint.

With these parameters as described and illustrated, a set of equationsare provided below that determine the three-dimensional shape of thelenticular cuts, assuming that the desired correction is purely defocus:

$\begin{matrix}{{Z_{1,L}\left( {x,y} \right)} = {{H + \frac{\delta_{C}}{2} + R_{1} - {\sqrt{R_{1}^{2} - x^{2} - y^{2}}\mspace{14mu} {for}\mspace{14mu} \sqrt{x^{2} + y^{2}}}} \leq \frac{D_{L}}{2}}} & {{Eq}.\mspace{14mu} (4)} \\{{Z_{2,L}\left( {x,y} \right)} = {{H - \frac{\delta_{C}}{2} - R_{2} + {\sqrt{R_{2}^{2} - x^{2} - y^{2}}\mspace{14mu} {for}\mspace{14mu} \sqrt{x^{2} + y^{2}}}} \leq \frac{D_{L}}{2}}} & {{Eq}.\mspace{14mu} (5)} \\{{Z_{1,T}\left( {x,y} \right)} = {{H + \delta_{E1} - {{\left( {\sqrt{x^{2} + y^{2}} - \frac{D_{L}}{2}} \right) \cdot \frac{\delta_{E1}}{\xi}}\mspace{14mu} {for}\mspace{14mu} \frac{D_{L}}{2}}} \leq \sqrt{x^{2} + y^{2}} \leq {\frac{D_{L}}{2} + \xi}}} & {{Eq}.\mspace{14mu} (6)} \\{{Z_{2,T}\left( {x,y} \right)} = {{H - \delta_{E2} + {{\left( {\sqrt{x^{2} + y^{2}} - \frac{D_{L}}{2}} \right) \cdot \frac{\delta_{E2}}{\xi}}\mspace{14mu} {for}\mspace{14mu} \frac{D_{L}}{2}}} \leq \sqrt{x^{2} + y^{2}} \leq {\frac{D_{L}}{2} + \xi}}} & {{Eq}.\mspace{14mu} (7)} \\{\delta_{E1} = {\frac{\delta_{C}}{2} + R_{1} - \sqrt{R_{1}^{2} - \left( \frac{D_{L}}{2} \right)^{2}}}} & {{Eq}.\mspace{14mu} (8)} \\{\delta_{E\; 2} = {\frac{\delta_{C}}{2} + R_{2} - \sqrt{R_{2}^{2} - \left( \frac{D_{L}}{2} \right)^{2}}}} & {{Eq}.\mspace{14mu} (9)}\end{matrix}$

The shape and dimensions of the cuts may include additional correctionfor higher order aberrations and may be computed from measured visionerrors. In some embodiments, approximately 50% of the total hyperopiccorrection is applied to each of the two mutually mirror-imaged cutsurfaces.

It is noted that the thickest portion of the concave lens cut isprovided at the intersection of the tapering zone and the concave lenscuts which correspond to a portion of the cornea that is thicker than acenter portion of the cornea. Consequently, from the standpoint ofcornea thickness, correcting hyperopia is more tolerable than correctingmyopia, where the thicker portion of the lens to be removed is at thecenter of the cornea, corresponding to a thinner portion of the cornea.

The shape of the tapering zone 1330 need not be linear in shape. Thetapering zone may be curved or any shape that minimizes light scatteringat the cutting junctions and optimizes the matching of the two cutsurfaces after lens extraction. The peripheral zone may be linear or ahigher order polynomial.

Some embodiments of the invention apply to single-spot scanning methodsapplied in femtosecond laser systems. The invention also applies tocornea incisions using UV 355 nm sub-nanosecond lasers.

For illustrative purposes, Equations (2), (8) and (9) are used toestimate the thickness of the concave lens. In a hyperopic correction ofΔD=5 diopter (which is high end values for LASIK hyperopia procedures)and assuming that a symmetric shape of the lenticule is selected,R₁=R₂=150.4 mm. Assuming D_(L)=7.0 mm and δ_(C)=10 μm, thenδ_(E)=δ_(E1)+δ_(E2)≈δ_(C)+D_(L) ²*ΔD/[8(n−1)]≈92 μm.

FIG. 14 illustrates an exemplary scanning process 1400 using a surgicalophthalmic laser system according to an embodiment of the presentinvention. FIG. 14 illustrates another embodiment of the“Fast-Scan-Slow-Sweep” scanning described previously. While performingan XY scan, Z values can be calculated from Eqs.(1)-(9), and the desiredthree-dimensional concave lens-shape cutting surfaces may be generated.

A top view of the lenticular incision illustrates three exemplary sweeps1430 (1A to 1B), (2A to 2B) and (3A to 3B), with each sweep goingthrough (i.e., going over) the concave lenticular incision 1410 andtapering zone 1420. In an embodiment, the lenticular incision isperformed in the following steps:

1. Calculate the radius of curvature based on the amount of correction,e.g., a hyperopic correction.

2. Select the diameter for the lenticular incision to be extracted.

3. Calculate the shape of the lenticular incisions (concave surface andtaper).

4. Perform the side incision first (not shown) to provide a vent for gasthat can be produced in the lenticular surface dissections. This is alsothe incision for the entry of forceps and for lens extraction.

5. Perform bottom surface dissection (the bottom dissection 1310 asshown in cross-sectional view). In doing so, the fast scan line ispreferably kept tangential to the parallels of latitude, and thetrajectory of the slow sweep drawn by X, Y, and Z scanning devices movesalong the meridians of longitude (near south pole in a sequence of 1A→1B(first sweep of lenticular cut), 2A→2B (second sweep of lenticular cut),3A→3B (third sweep of lenticular cut), and so on (4A), until the fullbottom dissection surface is generated.

6. Perform the top surface dissection 1320 in a similar manner as thebottom dissection is done. It is noted that the bottom dissection isdone first. Otherwise, the bubble generated during the top dissectionwill block the laser beam in making the bottom dissection.

FIG. 15 is a flowchart illustrating an exemplary surgery process 1500according to an embodiment of the present invention. The laser system 10may start a surgical procedure performing pre-operation measurements(Action Block 1510). For example, in an ophthalmologic surgery forhyperopic correction, the hyperopic diopter is determined, the SLOW_Zposition is determined, and so on. The laser system 10 calculates theshape of the incisions (Action Block 1520). The laser system 10calculates the radius of curvatures based on the amount of correction,e.g., the hyperopic correction determined in pre-operation measurements(Action Block 1530), as determined by Equations (4)-(8), for example.The laser system 10 first performs a side incision to provide a vent forgas that can be produced in the lenticular surface dissections, and fortissue extraction later on (Action Block 1540). The laser system 10 thenperforms the bottom lenticular surface dissection (Action Block 1550)before performing the top lenticular surface dissection (Action Block1560). Performing the dissections in this order allows gas to vent outof the cornea instead of becoming trapped in gas bubbles within thecornea. The lenticular tissue is then extracted (Action Block 1570).

Another embodiment for creating a lenticular incision for treatingmyopia, by cutting and extracting a convex lens-shaped stroma materialfrom a corneal, is described with reference to FIG. 16. FIG. 16 is aside cross-sectional view of the lenticular incision 1600 cut throughthe optical axis, where the vertical direction is the depth direction,parallel to the optical axis of the eye, and the horizontal direction isreferred to as the transverse direction. The lenticular incision 1600preferably has a circular shape in the front view of the eye. In someembodiments, the lenticular incision 1600 is rotationally symmetricalwith respect to the optical axis of the eye. The cornea from which thelenticule is incised and extracted is not shown. This procedure isintended to be performed using a patient interface (not shown) that doesnot employ a contact lens to press against the patient's cornea. Such apatient interface may employ, for example, a liquid that fills the spacebetween the patient's cornea and a lens of the patient interface. Thus,the cornea is in its natural shape during the creation of the lenticularincision.

The lenticular incision 1600 in this embodiment is similar to thelenticular incision 900 in the embodiment of FIG. 8, with the followingdifferences. The lenticular incision 900 in FIG. 8 is formed by a toplenticular surface and a bottom lenticular surface which are both convexspherical surfaces (i.e. each is a part of a sphere). In the lenticularincision 1600 of FIG. 16, each of the top and bottom lenticular surfaceshas a convex spherical portion CC′ or AA′ at the center, and aperipheral portion CD or AB, referred to as the edge transition portion.In the top view, the spherical portion preferably has a circular shapeand the edge transition portion has a ring shape that surrounds thespherical portion; the top and bottom spherical portions overlap eachother in the top view and the top and bottom edge transition portionsoverlap each other. While each of the top and bottom spherical portionsis a part of a sphere, the respective edge transition portion is notlocated on the same sphere of the spherical portion but rather, has asteeper shape in the side cross-sectional view than the sphere. In otherwords, each edge transition portion is located within the volume definedby the sphere of the corresponding spherical portion. Thus, the distancefrom the optical axis O of the lenticule to the intersection point G,where the top edge transition portion CD and the bottom edge transitionportion AB intersect each other, is smaller than the distance from theoptical axis O to the imaginary intersection point H′, where the twospheres that define the spherical portions CC′ and AA′ intersect eachother. Note that, in FIG. 16, the two intersection points areillustrated on the right-hand side edge of the lenticule 1600 andlabeled G′ and H′, respectively, where OG′<OH′.

The central portion of the lenticule 1600 insider the peripheries of thespherical portions CC′ and AA′ of the top and bottom lenticule surfacesconstitutes the optical zone of the lenticule; the optical power of theoptical zone is defined by the curvatures of the top and bottomspherical portions. Within the optical zone, a center layer, locatedbetween a transverse plane that pass through the circumference of thetop spherical portions CC′ and a transverse plane that pass through thecircumference of the bottom spherical portions AA′, which are indicatedby the two horizontal dashed lines in FIG. 16, constitutes anon-refractive layer as it does not contribute to the optical power ofthe optical zone.

In some preferred embodiment, the distance (denoted W_(G)) from theboundary of the optical zone (in FIG. 16, the line parallel to theoptical axis O and passing through the boundary C of the optical zone)to the intersection point G of the two edge transition portions isbetween 30% to 90% of the distance (denoted W_(H)) from the boundary ofthe optical zone to the imaginary intersection point H′, i.e.,30%<W_(G)/W_(H)<80%. In some preferred embodiment, in the sidecross-sectional view (e.g. FIG. 16), the edge transition portion CD is apart of an ellipse, with the major axis of the ellipse oriented parallelto the optical axis O and the minor axis perpendicular to the opticalaxis O. In such an example, the width of the edge transition portion(i.e. the distance W_(G)) can be adjusted by adjusting the minor axis ofthe ellipse.

The side cross-sectional profiles of the top and bottom edge transitionportions CD and AB are smooth functions, i.e., their first orderderivatives are continuous functions. Moreover, each of the top andbottom lenticular surface profiles is smooth at the point where thespherical portion CC′/AA′ joins the edge transition portion CD/AB. Inother words, the entire top lenticular surface is a smooth surface andthe entire bottom lenticular surface is a smooth surface. This reducestissue step formation in the cornea after the lenticule is extracted.

The top and bottom edge transition portions CD and AB are mirrorsymmetrical with respect to the center plane EF, which is the transverseplane that passes through the intersection circle of the top and bottomedge transition portions CD and AB. Thus, the top and bottom incisionsurfaces have equal area, so that they will match each other withoutcorneal striae after the lenticule is extracted. The top and bottomspherical portions CC′ and AA′ may be either mirror symmetrical or notmirror symmetrical with respect to the center plane EF.

The end points D and B of the top and bottom edge transition portions CDand AB extend beyond the intersection point G of the two edge transitionportions. This helps to ensure that the lenticule is fully separatedfrom the cornea, so that the extraction can be done free oftissue-bridges and minimal or no unwanted residual tissue pieces areleft inside the cornea. In this regard, the lenticular incision 1600 issimilar to the lenticular incision 900 of the embodiment of FIG. 8.

The lenticular incision 1600 of the embodiment of FIG. 16, with the edgetransition portions in the periphery of the lenticule, has the followingadvantages over the lenticular incision 900 of the embodiment of FIG. 8.First, comparing a lenticule 900 and a lenticule 1600 having the sameoptical zone diameter (the optical zone of the lenticule 900 is theentire lenticule with incision diameter 917 (DL) as shown in FIG. 8),the shape of the lenticule 1600 effectively adds the non-refractivelayer (a flat tissue disk of a certain thickness) to the lenticule. Thiscan help ensure that the overall lenticule is sufficiently thick for itto be extracted as a whole piece. This is particularly important for lowdiopter correction (for example, less than 2 diopters), as the overalllenticule would otherwise be too thin. Second, the shape of thelenticule 1600 in the embodiment of FIG. 16 also increases the thicknessof lenticule edge, due to the steeper profile in the edge transitionregions CD and AB. This helps to ensures that the lenticule edge issufficiently thick so it is much less likely to be torn duringextraction. Torn edge would leave irregularly shaped residual tissueedge in the cornea.

A lenticule with an abrupt edge, such as that shown in FIG. 17A, canalso solve the above two problems, by providing a lenticule edge with anon-zero thickness. Such a shape, however, has its own problems, one ofwhich being that it leads to corneal striae after the lenticule isextracted and a remaining abrupt step is left in the cornea, as shown inFIG. 17B. Such unwanted abrupt change in the tissue can cause unwantedlight scattering for the patient.

The lenticular incision 1600 of the embodiment of FIG. 16 solves theabove two problems without creating a remaining abrupt step in thecornea after extraction.

To summarize, the lenticular incision 1600 of the embodiment of FIG. 16has advantages over both the lenticular incision 900 of the embodimentof FIG. 8 and one with an abrupt edge as shown in FIG. 17A. Thelenticular incision 1600 provides a continuous edge transition in theincision without abrupt steps; it allows for smooth intrastromal tissuematching in the vicinity of the lenticule edge after the lenticule isextracted, which minimizes corneal striae and light scattering that canbe caused by abrupt tissue steps inside the cornea, and at the same timecreates a lenticule of a sufficient thickness to ensure successfulextraction.

The lenticular incision 1600 also has certain similarities with thehyperopia-correction lenticular incision 1200 and 1300 in the embodimentof FIGS. 12 and 13. Both the lenticular incision 1600 and the lenticularincision 1200/1300 has central portions of their top and bottomlenticular surfaces that are spherical, giving optical power to thelenticule, and peripheral portions that are not on the same sphericalsurface as the respective spherical portions, which serve as atransition region to avoid an abrupt edge and the problems associatedwith it.

FIG. 19 shows a variation of the lenticular incision 1200 or 1300 ofFIGS. 12 and 13. The lenticular incision 1900 here (only half of it isshown in FIG. 19) is similar to the incisions 1200 and 1300 in that ithas concave top and bottom surfaces 1920 and 1940, which are preferablyspherical surfaces, and which define the optical power of the lenticule;but unlike in the incisions 1200 and 1300, the top and bottom edgetransition portions 1930 and 1950 of the lenticular incision 1900 aresmooth surfaces without sharp corners or edges. In one embodiment, inthe side cross-sectional view (e.g. FIG. 19), the top edge transitionportion 1930 is a part of an ellipse 1960, which is shown in dashed linein FIG. 19, with the major axis of the ellipse oriented parallel to theoptical axis of the cornea and the minor axis perpendicular to theoptical axis. The concave top surface joins the ellipse smoothly.Similarly, the bottom edge transition portion 1950 is also a part ofanother ellipse (not shown in FIG. 19). Preferably, the top and bottomedge transition portions 1930 and 1950 are mirror symmetrical to eachother with respect to a transverse center plane perpendicular to theoptical axis of the eye, and the top and bottom edge transition portionsintersect each other at an intersection location and both extend beyondthe intersection location.

The lenticular incisions 1600 and 1900 may be formed using a surgicalophthalmic laser system and the “Fast-Scan-Slow-Sweep” scanning methoddescribed previously. The scanning method is similar to that of theembodiments of FIG. 8 an FIGS. 13 and 14, except that in the sidecross-sectional view the slow sweep follows the curve D-C-C′-D′ for thetop incision surface and the curve B-A-A′-B′ for the bottom incisionsurface. In the top view, the sweeps are similar to those shown in FIG.14, with exemplary sweeps 1A to 1B, 2A to 2B, and 3A to 3B, except thatthe central area 1410 would now indicate the spherical portion CC′/AA′(the optical zone), and the peripheral area 1420 would now indicate theedge transition portion CD/AB.

In an embodiment, the lenticular incision is performed in the followingsteps:

1. Calculate the radius of curvature of the spherical portions based onthe amount of correction, e.g., a myopic correction.

2. Select parameters of the lenticular incision to be extracted,including the diameter of the optical zone and the thickness of thenon-refractive layer.

3. Calculate the shape of the lenticular incisions (top and bottomspherical portions and top and bottom edge transition portions).

4. Perform the side incision first (not shown) to provide a vent for gasthat can be produced in the lenticular surface dissections. This is alsothe incision for the entry of forceps and for lens extraction.

5. Perform bottom surface dissection. In doing so, the fast scan line ispreferably kept tangential to the parallels of latitude (circles on thebottom lenticular surface that are perpendicular to and center at theoptical axis), and the trajectory of the slow sweep drawn by X, Y, and Zscanning devices moves along the meridians of longitude (the curvesformed by an intersection of the bottom lenticular surface with a sidecut plane that passes through the optical axis) near south pole in asequence of 1A to 1B (first sweep of lenticular cut), 2A to 2B (secondsweep of lenticular cut), 3A to 3B (third sweep of lenticular cut), andso on (4A), until the full bottom dissection surface is generated.

6. Perform the top surface dissection in a similar manner as the bottomdissection is done. It is noted that the bottom dissection is donefirst. Otherwise, the bubble generated during the top dissection willblock the laser beam in making the bottom dissection.

FIG. 18 is a flowchart illustrating an exemplary surgery process 1800according to an embodiment of the present invention. The laser system 10may start a surgical procedure performing pre-operation measurements(Action Block 1810). For example, in an ophthalmologic surgery formyopic correction, the myopic diopter is determined, the SLOW_Z positionis determined, and so on. The laser system 10 calculates the radius ofcurvatures of the spherical portions based on the amount of correction,e.g., the myopic correction determined in pre-operation measurements(Action Block 1820). The laser system 10 calculates the shape of theincisions, including the edge transition portions according to theembodiment of FIG. 16 (Action Block 1830). The laser system 10 firstperforms a side incision to provide a vent for gas that can be producedin the lenticular surface dissections, and for tissue extraction lateron (Action Block 1840). The laser system 10 then performs the bottomlenticular surface dissection (Action Block 1850) before performing thetop lenticular surface dissection (Action Block 1860). Performing thedissections in this order allows gas to vent out of the cornea insteadof becoming trapped in gas bubbles within the cornea. The lenticulartissue is then extracted (Action Block 1870).

In alternative embodiments, the optical zone of the lenticular incision1600 may have non-spherical components, such as a cylindrical componentor other higher order. In such a case, the central portion CC′ and AA′are no longer spherical, but the edge transition portions CD and ABstill have the characteristics that they are steeper than the extensionsof the central portions would be.

As described earlier, the lenticular incision 1600 is intended to beperformed using a patient interface that does not employ a contact lensto press against the patient's cornea, so that the cornea is in itsnatural shape during the creation of the lenticular incision. In analternative embodiment, the lenticular incision may be performed whileusing a patient interface that presses against the cornea with a curvedcontact lens surface. In this case, the profiles of the top and bottomedge transition portions are substantially symmetrical about a centercurved surface, rather than a transverse center plane. The shape of thecenter curved surface can be calculated from the shape of the contactlens surface, and is such that when the contact lens is removed from thepatient's eye and the cornea returns to its natural shape, the centercurved surface would become a transverse plane perpendicular to theoptical axis.

All patents and patent applications cited herein are hereby incorporatedby reference in their entirety.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made without departing from the spirit or scope of theinvention. Thus, it is intended that this disclosure cover allmodifications, alternative constructions, changes, substitutions,variations, as well as the combinations and arrangements of parts,structures, and steps that come within the spirit and scope of theinvention as generally expressed by the following claims and theirequivalents.

What is claimed is:
 1. An ophthalmic surgical laser system comprising: alaser delivery system for delivering a pulsed laser beam to a target ina subject's eye; an XY-scan device to deflect the pulsed laser beam; aZ-scan device to modify a depth of a focus of the pulsed laser beam; anda controller configured to control the XY-scan device and the Z-scandevice to form a top lenticular incision and a bottom lenticularincision of a lens in a cornea of the subject's eye, wherein the toplenticular incision has a top concave portion at a center and a top edgetransition portion that surrounds the top concave portion, the top edgetransition portion having a smooth convex shape and is smoothly joinedto the top concave portion, the top lenticular incision being a smoothsurface, wherein the bottom lenticular incision has a bottom concaveportion at a center and a bottom edge transition portion that surroundsthe bottom concave portion, the bottom edge transition portion having asmooth convex shape and is smoothly joined to the bottom concaveportion, the bottom lenticular incision being a smooth surface, whereinthe top and bottom edge transition portions are mirror symmetrical toeach other with respect to a transverse center plane perpendicular to anoptical axis of the eye.
 2. The ophthalmic surgical laser system ofclaim 1, wherein in a side cross-sectional view, the top edge transitionportion is a part of an ellipse, and the bottom edge transition portionis a part of another ellipse.
 3. The ophthalmic surgical laser system ofclaim 1, wherein the top and bottom edge transition portions intersecteach other at an intersection location and both extend beyond theintersection location.
 4. The ophthalmic surgical laser system of claim1, wherein the top concave portion is a part of a sphere and the bottomconcave portion is a part of another sphere.
 5. The ophthalmic surgicallaser system of claim 1, further comprising a resonant scanner.
 6. Theophthalmic surgical laser system of claim 1, wherein the XY-scan devicedeflects the pulsed laser beam to form a scan line.
 7. The ophthalmicsurgical laser system of claim 6, wherein the scan line is tangential tothe parallels of latitude of the lens, the parallels of latitude beingcircles on the top or bottom lenticular surface that are perpendicularto and center at the optical axis.
 8. The ophthalmic surgical lasersystem of claim 7, wherein the scan line is moved along the meridians oflongitude of the lens, the meridians of longitude being curves formed byan intersection of the top or bottom lenticular surface with side cutplanes that pass through the optical axis.
 9. The ophthalmic surgicallaser system of claim 8, wherein the top lenticular incision is movedover the top surface of the lens through an apex of the top surface ofthe lens, and the bottom lenticular incision is moved over the bottomsurface of the lens through an apex of bottom surface of the lens.
 10. Amethod for creating a lenticular incision using an ophthalmic surgicallaser system, the method comprising the steps of: generating a pulsedlaser beam; delivering the pulsed laser beam to a target in a subject'seye; deflecting, by an XY-scan device, the pulsed laser beam; modifying,by a Z-scan device, a depth of a focus of the pulsed laser beam; andcontrolling, by a controller, the XY-scan device and the Z-scan deviceto form a top lenticular incision and a bottom lenticular incision of alens in a cornea of the subject's eye, wherein the top lenticularincision has a top concave portion at a center and a top edge transitionportion that surrounds the top concave portion, the top edge transitionportion having a smooth convex shape and is smoothly joined to the topconcave portion, the top lenticular incision being a smooth surface,wherein the bottom lenticular incision has a bottom concave portion at acenter and a bottom edge transition portion that surrounds the bottomconcave portion, the bottom edge transition portion having a smoothconvex shape and is smoothly joined to the bottom concave portion, thebottom lenticular incision being a smooth surface, wherein the top andbottom edge transition portions are mirror symmetrical to each otherwith respect to a transverse center plane perpendicular to an opticalaxis of the eye.
 11. The method of claim 10, wherein in a sidecross-sectional view, the top edge transition portion is a part of anellipse, and the bottom edge transition portion is a part of anotherellipse.
 12. The method of claim 10, wherein the top and bottom edgetransition portions intersect each other at an intersection location andboth extend beyond the intersection location.
 13. The method of claim10, wherein the top concave portion is a part of a sphere and the bottomconcave portion is a part of another sphere.
 14. The method of claim 10,wherein the XY-scan device deflects the pulsed laser beam to form a scanline.
 15. The method of claim 14, wherein the scan line is tangential tothe parallels of latitude of the lens, the parallels of latitude beingcircles on the top or bottom lenticular surface that are perpendicularto and center at the optical axis.
 16. The method of claim 15, whereinthe scan line is moved along the meridians of longitude of the lens, themeridians of longitude being curves formed by an intersection of the topor bottom lenticular surface with side cut planes that pass through theoptical axis.
 17. The method of claim 16, wherein the top lenticularincision is moved over the top surface of the lens through an apex ofthe top surface of the lens, and the bottom lenticular incision is movedover the bottom surface of the lens through an apex of bottom surface ofthe lens.